Regular coffee consumption is associated with a lower risk of death and improved health outcomes, according to new research.

One of these health associations was a reduced risk of type 2 diabetes, with higher coffee intake more often linked to health benefits compared to no coffee and low coffee consumption.

University of Southampton scientists now want to understand whether the observed associations are causal, and further explore why coffee appears to have benefits for health.

The researchers assessed data from 201 meta-analyses that examined the associations between coffee consumption and any health outcome in adults, from any country or setting.

Intake of three to four cups a day compared to none indicated the largest risk reduction for type 2 diabetes, Alzheimer's disease, Parkinson's, depression, cancer and several other health problems.

Harmful associations were mostly nullified by suitable adjustment for smoking, except in pregnancy, while there was a link between coffee drinking and fracture risk in women but not men.

Lead author Robin Poole, MB, ChB, MSc, said: "It is important to systematically assess the totality of higher level evidence of the effects of coffee consumption on all health outcomes. This approach can help contextualize the magnitude of the association across health outcomes and importantly assess the existing research for any harm that could be associated with increased consumption.

In a related editorial, Eliseo Guallar, MD, MPH, Johns Hopkins Bloomberg School of Public Health, warned that doctors should not begin to recommend coffee to help prevent or treat health complications.

"The evidence is so robust and consistent across studies and health outcomes, however, that we can be reassured that drinking coffee is generally safe, although some caveats apply," said Guallar. "Additional studies are also needed to understand why people start and stop drinking coffee and the factors associated with coffee intake."